I had bowel cancer 4 years ago and now my doctor wants to test the tumour

Sometimes, testing the tumour itself can provide important clues as to whether the cancer was caused by a “faulty gene” that is being passed down through the family.

In colon cancer, a special stain can be applied to the tumour. If there is “loss of staining” for a particular protein, it may mean that the gene that makes that protein isn’t working.

This testing can be done on the tiny samples that labs store for many years after surgery.

The results of this test are just a guide.

For example, the change to the gene may have only happened that particular part of the bowel (the most common case). These types of changes are called somatic mutations and can’t be passed on.

Sometimes however, the genetic change came from a parent, either from the father via the sperm or the mother via the egg. This kind of change is called a germline mutation. Germline mutations can be inherited and may be associated with an increased risk of certain cancers.

Depending on the results, your doctor may refer you to a cancer genetics specialist to discuss the likelihood of an inherited genetic mutation and the benefits and limitations of a genetic test.